CI for Regression Testing & Benchmarking

[fpjentzsch]

Adds a regression testing and benchmarking suite to the GitLab CI, next to the existing unit test test suite. Includes:

• Benchmarking scripts that wrap the builder to perform gridsearches defined in a simple YAML format
• Infrastructure for running bitstreams on an FPGA board and logging all results via DVC
• New custom_step_library to collect all custom steps required for the included end2end models (stored via DVC)
• Extension of the validate.py script for on-board Top-1 accuracy validation on MNIST, CIFAR-10, CIFAR-100, ImageNet (if synthesized with IODMA shell)
• Changes to the logging infrastructure and launch_process_helper

See #76 for more information.

Depends on / includes:

• Introduce Live FIFO-Sizing #46, which includes Integrate Instrumentation into Zynq Backend #45